command line arguments problem

Hi,
I have to write a program which accepts a set of numbers and sort them in descending order and if "-r" is included in the command line then it should sort the numbers in ascending order.The program i wrote isn't working plz tell me what is wrong with it and how to correct it

Code:

---

# include <stdio.h>

main (argc, argv)
int argc;
char *argv[];
{
  int ar[100];
  int i, j, n, flag, temp;

  printf ("usage: a.out for descending order\n");
  printf ("usage: a.out -r for ascending order\n");
  printf ("enter the number of elements in array\n");
  scanf ("%d", &n);
  printf ("enter the elements of array\n");
  for (i = 0; i < n; i++)
  scanf ("%d", &ar[i]);
  if (*argv == "-r")
    {
    for (i = 0; i < n; i++)
        {
        for (j = 0; j < (n-i-1); j++)
            {
            if (ar[j] > ar[j+1])
              {
                temp = ar[j];
                ar[j] = ar[j+1];
                ar[j+1] = temp;
              }
            }
        }
    printf ("the sorted array is \n");
    for (i = 0; i < n; i++)
    printf ("%d\n", ar[i]);
    }
else
  {
    for (i = 0; i < n; i++)
      {
        for (j = 0; j < (n-i-1); j++)
            {
              if (ar[j] < ar[j+1])
                {
                temp = ar[j];
                ar[j] = ar[j+1];
                ar[j+1] = temp;
                }
            }
        }
    printf ("the sorted array is \n");
    for (i = 0; i < n; i++)
    printf ("%d\n", ar[i]);
  }
}

---

Two things wrong:

Code:

---

  if (*argv == "-r")

---

First, you probably want argv[1], not *argv (which is argv[0] using alternative syntax).

Second, you are comparing if argv[0] points to the string constant "-r" - which is very unlikely.

--
Mats

By the way, why are you using the old parameter declaration syntax?

I tried by placing

Code:

---

If (argv[1] == "-r")

---

and

Code:

---

if ((argv[1] == "-" )&& (argv[2] == "r"))

---

in place of the previous if statement but still it doesn't seem to work :(

You can't compare strings with the = sign. User strcmp().

Quote:

---

Originally Posted by abhiii

I tried by placing

Code:

---

If (argv[1] == "-r")

---

and

Code:

---

if ((argv[1] == "-" )&& (argv[2] == "r"))

---

in place of the previous if statement but still it doesn't seem to work :(

---

To compare strings, you need to use strcmp() [and note that it returns zero for "matches exactly").

Or you could do

Code:

---

(argv[1][0] == '-' && argv[1][1] == 'r')

---

--
Mats

Ninja'd

You are both slow.

It would probably be best to write:

Code:

---

if (argc > 1 && strcmp(argv[1], "-r") == 0)

---

Comparing the characters directly would allow say, -rags_to_riches (which might be fine, but the usage instructions only mention -r), unless a check if argv[1][2] == '\0' is performed.